(1) Field of the Invention
The present invention relates to a transmission apparatus in which cards are inserted into slots of a shelf and either a redundancy configuration or a non-redundancy configuration is used.
A variety of transmission apparatuses employ either a redundancy configuration or a non-redundancy configuration. When the redundancy configuration is used, a working card and a protection card per channel are installed in the transmission apparatus. If the working card malfunctions, the working card is disconnected from a transmission line and the protection card is connected to the line, in order to provide reliability of data transmitted through the transmission apparatus. When the non-redundancy configuration is used, a single card per channel is installed in the transmission apparatus. The non-redundancy configuration is often used by transmission apparatuses which do not require high reliability of the data transmitted. It is desirable to suitably select the redundancy configuration or the non-redundancy configuration for each transmission apparatus in order to meet both the reliability and the cost efficiency.
(2) Description of the Related Art
FIG. 6 shows a conventional transmission apparatus with a working card connected to a transmission line.
In the conventional transmission apparatus of FIG. 6, a plurality of cards are inserted into slots of a shelf 51. A working card 52-1 and a protection card 52-2 are inserted in the slots of the shelf 51. The working card 52-1 contains a relay 53-1, and the relay 53-1 is switched as indicated by the dotted line in FIG. 6 so as to connect the working card 52-1 to a transmission line 55. The protection card 52-2 contains a relay 53-2, and the relay 53-2 is switched as indicated by the dotted line in FIG. 6 so as to connect the protection card 52-2 to an inactive line. The shelf 51 includes a selector switch 54 at the outputs of the slots, and the selector switch 54 is switched as indicated by the dotted line in FIG. 6 so as to connect the output of the working card 52-1 to an output transmission line.
With the arrangement of the conventional transmission apparatus shown in FIG. 6, a signal supplied via the transmission line 55 is processed by the working card 52-1, and the processed signal is delivered from the working card 52-1 to the output transmission line. The working card 52-1 and the protection card 52-2 are usually configured in the form of a module of electronic parts fabricated on a printed circuit board. Alternatively, these cards may be called boards or units.
If the working card 52-1 in the above-mentioned apparatus malfunctions, the switching of the relays 53-1 and 53-2 and the switch 54 is changed to disconnect the working card 52-1 from the transmission line 55 and connect the protection card 52-2 to the transmission line 55.
FIG. 7 shows the conventional transmission apparatus with the protection card 52-2 connected to the transmission line 55.
As shown in FIG. 7, the relay 53-1 is switched as indicated by the dotted line in FIG. 7 so as to disconnect the working card 52-1 from the transmission line 55 and connect the working card 52-1 to an inactive line. The relay 53-2 is switched as indicated by the dotted line in FIG. 7 so as to connect the protection card 52-2 to the transmission line 55. The selector switch 54 is switched as indicated by the dotted line in FIG. 7 so as to connect the output of the protection card 52-2 to the output transmission line. With the arrangement of the conventional transmission apparatus shown in FIG. 7, a signal supplied through the transmission line 55 to the shelf 51 is processed by the protection card 52-2, and the processed signal is delivered from the protection card 52-2 to the output transmission line.
FIG. 8 shows a redundancy configuration and a non-redundancy configuration of a conventional transmission apparatus. In FIG. 8, "W" indicates a working card inserted in the shelf, "P" indicates a protection card inserted in the shelf, and "C" indicates a control card inserted in the shelf.
As shown in FIG. 8, the shelf is divided into an upper segment with eleven slots and a lower segment with eleven slots. In the upper segment of the shelf, ten sets of working cards "W" and protection cards "P" and a control card "C" are inserted into the slots thereof. The working card "W" and the protection card "P" of each set are installed per channel. The upper segment uses the redundancy configuration. In the lower segment of the shelf, five working cards "W", a protection card "P" and a control card "C" are inserted into the slots thereof. Either of the working card "W" and the protection card "P" is installed per channel. The lower segment mainly uses the non-redundancy configuration.
When the redundancy configuration, such as that of the upper segment of FIG. 8, is used, it is possible to make effective use of the card slots of the shelf. However, when the non-redundancy configuration, such as that of the lower segment of FIG. 8, is used, the number of vacant slots for the protection cards is increased with increase of the working cards inserted in the shelf. It is difficult for the conventional transmission apparatus to effectively use the vacant slots for the protection cards of the shelf in the non-redundancy configuration.
In order to effectively use the vacant slots for the protection cards in the shelf of the conventional transmission apparatus in the non-redundancy configuration, the line connections of the relays of the cards to be inserted (and those of the adjacent cards already inserted) have to be set such that the transmission line is always connected to the cards inserted as shown in FIG. 7. Such setting of the line connections of the relays has been manually performed for each of the cards inserted in the shelf. Practically the setting of the line connections of the cards inserted needs complicated and time-consuming manipulations, and erroneous setting of the line connections of the cards inserted in the shelf is likely to occur.